No abstract

Superparamagnetic maghemite (γ-Fe 2 O 3 ) nanoparticles of tunable diameters and silica-coated maghemite (SiO 2 /γ-Fe 2 O 3 ) nanoparticles of controllable morphology were successfully synthesized using a one-step flame spray pyrolysis (FSP) technique. The physical, chemical, and magnetic properties of γ-Fe 2 O 3 and SiO 2 /γ-Fe 2 O 3 nanostructures were characterized and compared with those of silica-coated FSP γ-Fe 2 O 3 produced by a conventional sol-gel method. Bovine serum albumin (BSA) adsorption-desorption was investigated as a model to demonstrate the feasibility of synthesized superparamagnetic nanoparticles for bioadsorption and bioseparation. Protein adsorption was observed to follow the Langmuir isotherm, with the highest binding capacity of 348 mg of BSA/g of particle and a dissociation constant of 0.0159 g/L attainable for FSP γ-Fe 2 O 3 (d XRD ) 14 nm) in 10 mM formate buffer. Electrostatically governed BSA orientations were proposed for different particle-buffer systems. Shifting the pH of suspension with K 2 HPO 4 enabled effective recovery of adsorbed BSA.

The genes encoding yeast old yellow enzymes (OYE 1, 2, and 3) and NAD(P)H-dependent 2-cyclohexen-1-one reductase from Zymomonas mobilis (NCR) were expressed separately in Escherichia coli. All four recombinant strains reduced the carbon double bond in alpha,beta-unsaturated alkenals and alkenones, however rates and enantio-specificities differed. Which of the two possible enantiomers was predominantly formed, was not only dependent on the choice of enzyme but also on the substrate: In addition to a dependency on methylation in alpha- or beta-position, the data of this study illustrate that firstly the E- or Z-configuration (cis- or trans-) of the carbon double-bond and secondly the remainder of the substrate molecule play roles in determining enantio-specificity. Based on the currently accepted mechanism of flavin mediated anti-hydrogenation of the carbon double bond, the data in this study may be explained by a flipped orientation of some of the substrates in the active center of OYE.